I have never done this, but I have heard of it being done. You'd want to stretch out the bellows as far as they'll go so you have essentially a flat surface to glue to. Then you'd have to work the folds back into place after gluing on the outer layer.
Originally Posted by RAP
The problem is that now you have 3 layers so it's thicker and won't compress as tightly as the original. Also, you'll need to use a light-tight outer layer. My understanding is that in building a new bellows you don't worry so much about this and rely on the inner layer to provide the light-tightness.
You'll want to use a very thin light-tight material, probably some type of rubber/vinyl coated cloth.